The invention relates to an apparatus for preventing unintentional bending in or jackknifing and for improving the lateral travelling stability under critical road and travelling conditions, which is located in the fulcrum area of an articulated vehicle comprising a front vehicle part and a rear vehicle part connected in articulated manner thereto, one of the two vehicle parts being motor-driven and suitable for semitrailers, articulated buses or vehicles having a towed vehicle part.
Articulated vehicles, such as e.g. semitrailers, comprise a towing vehicle and a following trailer pivotably coupled thereto. This towed part carries the load and transfers its mass by means of one or more axles directly to the road and indirectly and proportionately via the axles of the towing vehicle or front vehicle.
As a result of the articulated connection, the vehicle is sensitive with regards to its lateral travelling stability. In the case of semitrailers, the ratio of the towing vehicle wheel base to dimension from the supporting fulcrum to the centre of the rear axle unit is generally approximately 1:2. However, as a result of the design, the mass centre is relatively high and is located between the towing vehicle rear axle and the rear axle unit of the towed vehicle. During acceleration and deceleration when travelling, this can lead to an unstable behaviour of the overall vehicle. The frictional connection between the wheels and the road is of considerable significance, particularly if there are large adhesion differences between the different wheels or axles. As a function of the travelling speed, there is a danger of horizontal, undesired jackknifing of the articulated vehicle on braking or swerving of the semitrailer.
Under normal frictional connection conditions, the travelling pattern on a horizontal plane leads to clearly defined relationships between the steering lock of the front axle and the jackknifing angle of the semitrailer at its supporting fulcrum, which also leads to the curving of the vehicle. However, with increasing speed, the permitted steering lock on the front axle must be kept smaller for safety reasons, leading to the associated angle at the fulcrum of the semitrailer.
An articulated vehicle, such as e.g. a semitrailer, can jackknife for the following reasons:
different adhesion forces in the travelling pattern and mass forces, PA1 at excessive speed, mass forces via a lever action, PA1 skidding in the case of inadequate transverse adhesion.